101. Which rule is most important when choosing the parent chain for naming an alcohol by IUPAC system?
ⓐ. Select the chain with maximum branching first.
ⓑ. Select the chain with the greatest number of halogens.
ⓒ. Select the longest chain containing the \(OH\) group.
ⓓ. Select the chain with the lowest molecular mass.
Correct Answer: Select the longest chain containing the \(OH\) group.
Explanation: In IUPAC naming of alcohols, the parent hydrocarbon chain must include the carbon bearing the \(OH\) group. A longer chain that excludes the \(OH\)-bearing carbon cannot be chosen as the parent chain for the alcohol name. After selecting the proper parent chain, the suffix “-ol” is used. This rule ensures that the principal functional group is included in the main structure being named.
102. What is the IUPAC name of \(CH_3CH_2CH_2OH\)?
ⓐ. Propan-\(1\)-ol
ⓑ. Propan-\(2\)-ol
ⓒ. Ethanol
ⓓ. Butan-\(1\)-ol
Correct Answer: Propan-\(1\)-ol
Explanation: The molecule \(CH_3CH_2CH_2OH\) contains a three-carbon chain, so the parent hydrocarbon is propane. The \(OH\) group is attached to the first carbon when numbering begins from the end nearer to \(OH\). Therefore the suffix becomes “-ol” with locant \(1\). The name is propan-\(1\)-ol.
103. What is the IUPAC name of \(CH_3CH(OH)CH_3\)?
ⓐ. Propan-\(1\)-ol
ⓑ. Ethanol
ⓒ. Butan-\(2\)-ol
ⓓ. Propan-\(2\)-ol
Correct Answer: Propan-\(2\)-ol
Explanation: The parent chain has three carbon atoms, so the base name comes from propane. The \(OH\) group is attached to the middle carbon. Numbering from either end places the \(OH\) group at carbon \(2\). Hence the correct IUPAC name is propan-\(2\)-ol.
104. Which name correctly applies to \(CH_3CH_2CH(OH)CH_3\)?
ⓐ. Butan-\(1\)-ol
ⓑ. Butan-\(2\)-ol
ⓒ. Propan-\(2\)-ol
ⓓ. Pentan-\(2\)-ol
Correct Answer: Butan-\(2\)-ol
Explanation: The structure \(CH_3CH_2CH(OH)CH_3\) contains a four-carbon parent chain. Numbering must give the \(OH\) group the lowest possible locant. Starting from the right places the hydroxyl group on carbon \(2\), while starting from the left would place it on carbon \(3\). Therefore the name is butan-\(2\)-ol.
105. Which IUPAC name is correct for \(CH_3CH_2CH_2CH_2OH\)?
ⓐ. Butan-\(2\)-ol
ⓑ. Propan-\(1\)-ol
ⓒ. Pentan-\(1\)-ol
ⓓ. Butan-\(1\)-ol
Correct Answer: Butan-\(1\)-ol
Explanation: The longest chain containing the \(OH\) group has four carbon atoms, so the parent hydrocarbon is butane. Numbering begins at the end nearest the hydroxyl group. The \(OH\) group is on carbon \(1\), so the name becomes butan-\(1\)-ol. Naming it butan-\(2\)-ol would place the hydroxyl group on the wrong carbon.
106. Which structure corresponds to butan-\(2\)-ol?
ⓐ. \(CH_3CH_2CH_2CH_2OH\)
ⓑ. \(CH_3OCH_2CH_2CH_3\)
ⓒ. \(CH_3CH(OH)CH_2CH_3\)
ⓓ. \((CH_3)_3COH\)
Correct Answer: \(CH_3CH(OH)CH_2CH_3\)
Explanation: Butan-\(2\)-ol must have a four-carbon chain with the \(OH\) group on carbon \(2\). The structure \(CH_3CH(OH)CH_2CH_3\) satisfies both conditions. \(CH_3CH_2CH_2CH_2OH\) is butan-\(1\)-ol because the hydroxyl group is at the end. \(CH_3OCH_2CH_2CH_3\) is an ether, not an alcohol.
107. What is the IUPAC name of \(HOCH_2CH_2OH\)?
ⓐ. Ethane-\(1,2\)-diol
ⓑ. Ethanol
ⓒ. Propane-\(1,2\)-diol
ⓓ. Ethane-\(1\)-ol
Correct Answer: Ethane-\(1,2\)-diol
Explanation: The molecule \(HOCH_2CH_2OH\) contains two carbon atoms, so the parent hydrocarbon is ethane. There are two hydroxyl groups, one on carbon \(1\) and one on carbon \(2\). For two hydroxyl groups, the suffix “-diol” is used. Therefore the correct name is ethane-\(1,2\)-diol.
108. What is the IUPAC name of \(HOCH_2CHOHCH_2OH\)?
ⓐ. Propan-\(1\)-ol
ⓑ. Propane-\(1,2,3\)-triol
ⓒ. Propane-\(1,3\)-diol
ⓓ. Butane-\(1,2,3,4\)-tetrol
Correct Answer: Propane-\(1,2,3\)-triol
Explanation: The structure \(HOCH_2CHOHCH_2OH\) has a three-carbon chain. Each carbon bears one hydroxyl group, giving hydroxyl locants \(1\), \(2\), and \(3\). Since there are three \(OH\) groups, the suffix “-triol” is used. The correct IUPAC name is propane-\(1,2,3\)-triol.
109. Which IUPAC suffix is used for an alcohol containing two hydroxyl groups?
ⓐ. -one
ⓑ. -al
ⓒ. -diol
ⓓ. -ether
Correct Answer: -diol
Explanation: The suffix “-diol” is used when a compound contains two alcoholic hydroxyl groups. The locants of both \(OH\) groups must be shown in the name when needed. For example, \(HOCH_2CH_2OH\) is named ethane-\(1,2\)-diol. A single \(OH\) group uses “-ol,” while three hydroxyl groups use “-triol.”
110. Which name correctly gives the lowest locant to the hydroxyl group?
ⓐ. Pentan-\(4\)-ol
ⓑ. Butan-\(3\)-ol
ⓒ. Hexan-\(5\)-ol
ⓓ. Pentan-\(2\)-ol
Correct Answer: Pentan-\(2\)-ol
Explanation: In alcohol naming, the chain is numbered so that the carbon bearing \(OH\) gets the lowest possible number. A name such as pentan-\(4\)-ol would usually be renumbered from the opposite end to become pentan-\(2\)-ol. Similarly, butan-\(3\)-ol is named butan-\(2\)-ol by proper numbering. Pentan-\(2\)-ol follows the lowest-locant rule.
111. What is the IUPAC name of \(CH_3CH(CH_3)CH_2OH\)?
ⓐ. \(2\)-methylbutan-\(1\)-ol
ⓑ. \(2\)-methylpropan-\(1\)-ol
ⓒ. \(3\)-methylpropan-\(1\)-ol
ⓓ. \(1\)-methylpropan-\(2\)-ol
Correct Answer: \(2\)-methylpropan-\(1\)-ol
Explanation: The longest chain containing the \(OH\)-bearing carbon has three carbon atoms, so the parent is propan-\(1\)-ol. The \(OH\) group is on carbon \(1\), and a methyl substituent is attached to carbon \(2\). The name must show both the hydroxyl locant and the substituent locant. Thus \(CH_3CH(CH_3)CH_2OH\) is \(2\)-methylpropan-\(1\)-ol.
112. Which structure matches \(2\)-methylpropan-\(2\)-ol?
ⓐ. \((CH_3)_3COH\)
ⓑ. \(CH_3CH_2CH_2OH\)
ⓒ. \(CH_3CH(OH)CH_3\)
ⓓ. \(HOCH_2CH_2OH\)
Correct Answer: \((CH_3)_3COH\)
Explanation: \(2\)-methylpropan-\(2\)-ol has a propane parent chain with both the \(OH\) group and a methyl substituent on carbon \(2\). This gives a central carbon bonded to three methyl groups and one \(OH\) group. The condensed structure is \((CH_3)_3COH\). This structure is also known as tert-butyl alcohol in common naming.
113. Which name is incorrect because it does not give the \(OH\) group the lowest possible locant?
ⓐ. Propan-\(2\)-ol
ⓑ. Butan-\(2\)-ol
ⓒ. Hexan-\(2\)-ol
ⓓ. Butan-\(3\)-ol
Correct Answer: Butan-\(3\)-ol
Explanation: In a four-carbon chain, numbering from the nearer end should give the \(OH\) group the lowest locant. If the \(OH\) group appears to be at carbon \(3\), numbering from the opposite end places it at carbon \(2\). Therefore butan-\(3\)-ol is not the preferred IUPAC name. The proper name for that structure is butan-\(2\)-ol.
114. Which name is suitable for \(CH_2=CHCH_2OH\)?
ⓐ. Propan-\(1\)-ol
ⓑ. Prop-\(1\)-en-\(3\)-ol
ⓒ. Prop-\(2\)-en-\(1\)-ol
ⓓ. Propan-\(2\)-ol
Correct Answer: Prop-\(2\)-en-\(1\)-ol
Explanation: The parent chain has three carbon atoms and contains both the \(OH\) group and a double bond. The \(OH\) group is the principal suffix group here, so numbering begins from the end nearer to \(OH\). This places \(OH\) at carbon \(1\) and the double bond between carbons \(2\) and \(3\). The correct name is prop-\(2\)-en-\(1\)-ol.
115. Which statement about naming alcohols with unsaturation is correct?
ⓐ. The parent chain is chosen by ignoring the carbon bearing \(OH\).
ⓑ. The double bond always receives carbon \(1\), even if \(OH\) gets a higher number.
ⓒ. The suffix “-ol” is removed whenever a double bond is present.
ⓓ. The \(OH\) group receives priority for the lowest locant over a double bond.
Correct Answer: The \(OH\) group receives priority for the lowest locant over a double bond.
Explanation: When an alcohol contains both a double bond and a hydroxyl group, the parent chain must contain the \(OH\)-bearing carbon. Numbering is done so that the hydroxyl group receives the lowest possible locant. The double bond is still shown in the name using “en,” but it does not override the principal alcohol suffix. This is why names such as prop-\(2\)-en-\(1\)-ol are formed.
116. What is the IUPAC name of \(CH_3CH(OH)CH_2CH_2CH_3\)?
ⓐ. Pentan-\(4\)-ol
ⓑ. Pentan-\(2\)-ol
ⓒ. Butan-\(2\)-ol
ⓓ. \(2\)-methylbutan-\(1\)-ol
Correct Answer: Pentan-\(2\)-ol
Explanation: The longest chain containing the hydroxyl group has five carbon atoms, so the parent hydrocarbon is pentane. Numbering from the end closer to \(OH\) places the hydroxyl group at carbon \(2\). Numbering from the other end would place it at carbon \(4\), which is not preferred. Therefore the correct name is pentan-\(2\)-ol.
117. Which name correctly represents a compound with four carbon atoms and two hydroxyl groups at carbons \(1\) and \(3\)?
ⓐ. Butane-\(1,4\)-diol
ⓑ. Propane-\(1,3\)-diol
ⓒ. Butane-\(1,3\)-diol
ⓓ. Butan-\(3\)-ol
Correct Answer: Butane-\(1,3\)-diol
Explanation: Four carbon atoms give the parent name butane. Two hydroxyl groups require the suffix “-diol.” The locants \(1\) and \(3\) must be included to show the positions of the two \(OH\) groups. Hence the correct name is butane-\(1,3\)-diol.
118. Which structural formula corresponds to ethane-\(1,2\)-diol?
ⓐ. \(HOCH_2CH_2OH\)
ⓑ. \(CH_3CH_2OH\)
ⓒ. \(CH_3OCH_3\)
ⓓ. \(CH_3CHOHCH_3\)
Correct Answer: \(HOCH_2CH_2OH\)
Explanation: Ethane-\(1,2\)-diol has a two-carbon chain and two hydroxyl groups. The locants \(1\) and \(2\) mean one \(OH\) group is attached to each carbon. This gives the structure \(HOCH_2CH_2OH\). \(CH_3CH_2OH\) has only one hydroxyl group, and \(CH_3OCH_3\) is an ether.
119. Which IUPAC name is most appropriate for \(CH_3CH(OH)CH(CH_3)CH_3\)?
ⓐ. \(2\)-methylbutan-\(3\)-ol
ⓑ. \(3\)-methylbutan-\(3\)-ol
ⓒ. \(3\)-methylbutan-\(2\)-ol
ⓓ. \(2\)-ethylpropan-\(1\)-ol
Correct Answer: \(3\)-methylbutan-\(2\)-ol
Explanation: The longest chain containing the \(OH\)-bearing carbon has four carbon atoms. Numbering is chosen so that the \(OH\) group gets the lowest locant, placing it at carbon \(2\). The methyl substituent is then located at carbon \(3\). Therefore the correct name is \(3\)-methylbutan-\(2\)-ol.
120. Which naming decision is correct for \(CH_3CH_2CH(CH_3)CH_2OH\)?
ⓐ. Parent chain is propane because it has a branch.
ⓑ. Parent chain is butane because it includes \(OH\).
ⓒ. Parent chain is methylpropane because it is branched.
ⓓ. Parent chain is ethane because \(CH_2OH\) is terminal.
Correct Answer: Parent chain is butane because it includes \(OH\).
Explanation: The chosen parent chain must contain the carbon attached to \(OH\). In \(CH_3CH_2CH(CH_3)CH_2OH\), the longest chain including that carbon has four carbon atoms. Numbering begins at the \(CH_2OH\) end, giving the \(OH\) group locant \(1\). The full name would be \(2\)-methylbutan-\(1\)-ol.
